Effective solid waste management strategies are recognized as efforts to achieve campus sustainability. The university campus is currently considered the center of various activities involving students, lecturers, staff, and other parties contributing to the consumption pattern of energy, water, and other resources. This study aims to estimate the quantity and compositions of waste generated on the Universitas Diponegoro (UNDIP) campus, identify the causes of waste generation, evaluate the relationships between variables through statistical analysis, and recommend possible strategies to reduce solid waste generation. The results show that the simultaneous contribution of the student-gender ratio, student awareness level, administrative staff background, and green space amounted to 67.7% of the waste generation at UNDIP. Therefore, these four factors need to be a concern for campus authorities in their efforts to handle campus waste. Student awareness in particular was determined to be the only factor that significantly affects solid waste generation. UNDIP may implement proper environmental education through sustainability courses in each faculty to reduce solid waste in higher education institutions since it has the most significant impact. Outcomes of this study could be used as a reference to develop sustainable campus strategies, recycling plans, and comprehensive waste management in higher education.

This study focuses on improving heat transfer from the surface of heated tubes to airflow in the channel. Perforated concave delta winglet vortex generators, which have not been used in previous studies, were implemented in this study to increase the heat transfer rate. In this experimental study, the comparison of perforated concave delta winglet and perforated delta winglet was investigated in terms of increased heat transfer from a heated six-tube surface to the flow in a rectangular channel. The experimental results indicated that the use of perforated concave delta winglet vortex generators could increase the heat transfer rate of 46.3% toward the baseline. However, the optimal thermal-hydraulic performance was found in the use of the concave delta winglet at 1.37 with a staggered vortex generators arrangement. The results of this study indicated that the use of perforated vortex generators could reduce the pressure drop with a slight decrease in the heat transfer rate.

Various studies have been conducted to improve the tribological performance of thrust bearings. In the present study, thermohydrodynamic (THD) analysis was carried out to explore the performance of textured thrust bearings with rectangular dimples in three dimensions, considering turbulence and cavitation. Various models are available for predicting turbulence. Owing to disparities in forcing viscosity, velocity fluctuation, and parameter estimation, the performance of these models is typically distinct. Model comparison is the simplest method for identifying the strengths, limitations, and sources of uncertainty in a model. In this study, the k-ω turbulence model was of particular interest. Four k-ω models, namely, the standard k-ω model, BSL (Baseline) k-ω model, SST (shear-stress transport) k-ω model, and GEKO (Generalized k-Omega) k-ω model, were evaluated to predict the bearing characteristics. In this study, not only the tribological performance but also the acoustic characteristics were investigated. To capture more realistic phenomena, a multiphase mixture cavitation model was used to analyze the cavitation behavior of the lubricant. The results of this study show a comparison of the tribological performance between each turbulence model while considering the presence of cavitation and thermal conditions on the thrust bearing. In addition, the performance of thrust bearings under laminar flow conditions without cavitation was compared with these results. By comparing the various models, the necessity of incorporating turbulence and cavitation-coupled effects was confirmed. The main results also show that in the case of the BSL and standard k-ω turbulence models.

Population growth is correlated with the increasing demand for resources, such as fuel. The utilization of landfill passive zone mines as raw material for refuse-derived fuels (RDF) can be an alternative to meet fuel needs. However, mining results are dominated by combustible waste so that the concentration of methane gas decreases below 40% and causes a decrease in the financial aspect. Therefore, this study aims to determine the existing conditions of passive zones one and two and analyze the technical, environmental, and financial feasibility aspects of the RDF plant carried out at the Jatibarang landfill. Data were taken via field sampling and interviews with experts. The treated waste can produce a calorific value of 2,980 kcal/kg. Besides, there is a reduction in the amount of waste that goes to the landfill by 30,300 tons per year. The net profit obtained after the loan period ends is Rp. 12,703,795,674. The RDF plant at the Jatibarang landfill is feasible to run in view of the technical, environmental, and financial aspects.

The growth of diesel vehicles has consequences for the consumption of diesel oil. Therefore, using Jatropha as an alternative fuel reduces dependence on diesel oil and it does not interfere with food availability. However, the high viscosity of jatropha oil makes the fuel pump work harder. In addition, the low calorific value reduces the quality of the fuel which creates unique problems. Ethanol, with its low viscosity and high oxygen content, is expected to be effective in reducing jatropha problems for diesel engines. Therefore, this study aims to evaluate the addition of ethanol to the brake torque, brake-specific fuel consumption, exhaust gas temperature, and smoke opacity. The 4JB1 diesel engine with an EGR was tested on a 10% (DJ10) and 20% (DJ20) diesel-jatropha mixture. The experimental results showed that brake torque increased by 1.51% in the DJ10 application, brake specific fuel consumption decreased by 7.05%, exhaust gas temperature decreased by 0.67%, and smoke opacity increased by 25.91%. While in the DJ20 application, brake torque increased by 3.19%, brake-specific fuel consumption decreased by 30.08%, exhaust gas temperature decreased by 0.67%, and smoke opacity increased by 69.03%.